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B12 Supplements


Updated June 19, 2014

Vitamin B12 & Energy:

B vitamins are essential for energy production, and a few (but limited) studies suggest low B12 levels may be involved in fibromyalgia and chronic fatigue syndrome.

Vitamin B12 Dosage:

Some experts on fibromyalgia and chronic fatigue syndrome recommend at least 50 mg daily of most B vitamins, and 500 micrograms of B12. Some treatment protocols use B12 injections.

Many doctors disagree with this and consider B12 injections archaic and unscientific. Some doctors and researchers, however, say anecdotal evidence supports higher B12 levels for people with these conditions.

B12 in Your Diet:

You get B12 in your diet through almost any animal-derived food (meat, eggs, dairy). Some vegetarian products are fortified with B12, since a plant-based diet generally will not contain enough.

B12 Side Effects:

The most common side effect of vitamin B12 is mild, temporary diarrhea. Severe side effects, for which you should seek medical attention right away, include:
  • Severe allergic reactions
  • Calf pain, swelling or tenderness
  • Chest pain
  • Feel of swelling throughout body
  • Fever, chills or persistent sore throat
  • Irregular heartbeat
  • Muscle weakness or cramping
  • Shortness of breath
  • Unusual bruising or bleeding

More Supplement Information


Drugs.com. All rights reserved. "Cyanocobalamin (B12) Side Effects"

Scandinavian Journal of Rheumatology. 1997, vol. 26, no4, pp. 301-307. All rights reserved. "Increased concentrations of homocysteine in the cerebrospinal fluid in patients with fibromyalgia and chronic fatigue syndrome."

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